scholarly journals Atomic scale modelling of hexagonal structured metallic fission product alloys

2015 ◽  
Vol 2 (4) ◽  
pp. 140292 ◽  
Author(s):  
S. C. Middleburgh ◽  
D. M. King ◽  
G. R. Lumpkin
Keyword(s):  
Density Functional ◽  
Configurational Entropy ◽  
Principal Component ◽  
Atomic Scale ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Scale Modelling ◽  
Entropy Effects ◽  
Mo Content ◽  
The Impact

Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance.

scholarly journals A First-Principles Study of Hydrogen Desorption from High Entropy Alloy TiZrVMoNb Hydride Surface

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 553
Author(s):  
Jinjing Zhang ◽  
Jutao Hu ◽  
Haiyan Xiao ◽  
Huahai Shen ◽  
Lei Xie ◽  
...  
Keyword(s):  
Density Functional ◽  
Underlying Mechanism ◽  
Hydrogen Desorption ◽  
High Entropy Alloy ◽  
Hydrogen Atoms ◽  
Desorption Process ◽  
High Entropy ◽  
The Density Functional Theory ◽  
Hydride Hydrogen ◽  
Atomic States

The desorption behaviors of hydrogen from high entropy alloy TiZrVMoNb hydride surface have been investigated using the density functional theory. The (110) surface has been determined to be the most preferable surface for hydrogen desorption from TiZrVMoNb hydride. Due to the high lattice distortion and heterogeneous chemical environment in HEA hydride, hydrogen desorption from the HEA hydride surface is found to be complex. A comparison of molecular and atomic hydrogen desorption reveals that hydrogen prefers to desorb in atomic states from TiZrVMoNb hydride (110) surface rather than molecular states during the hydrogen desorption process. To combine as H2 molecules, the hydrogen atoms need to overcome attractive interaction from TiZrVMoNb hydride (110) surface. These results suggest that the hydrogen desorption on TiZrVMoNb hydride (110) surface is a chemical process. The presented results provide fundamental insights into the underlying mechanism for hydrogen desorption from HEA hydride surface and may open up more possibilities for designing HEAs with excellent hydrogen desorption ability.

Study on the effect of temperature and strain rate on Ni2FeCrCuAl high entropy alloy: a molecular dynamics study

2021 ◽  
Vol 3 (4) ◽  
pp. 045042
Author(s):  
S Gowthaman ◽  
T Jagadeesha
Keyword(s):  
Molecular Dynamics ◽  
Strain Rate ◽  
Point Defects ◽  
Tensile Deformation ◽  
Variable Temperature ◽  
Effect Of Temperature ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Beneficial Impact ◽  
The Impact

Abstract High entropy alloy has offered significant attention in various material science applications, due to its excellent material features. In this investigation, the mechanical characteristics of Ni2FeCrCuAl High Entropy Alloy (HEA) have been examined under variable temperature and strain rates to analyze its influence over the material features of high entropy alloy through Molecular Dynamics (MD) simulation and it is stated that the formation of various point defects and dislocations are the major cause for the augmentation of tensile deformation which impacts the tensile behavior of high entropy alloy. Moreover, the Radial Distribution Function (RDF) has been examined throughout tensile deformation, to investigate the impact of applied stress over the de-bonding of various atoms and it is found that the strain rate has a greater beneficial impact over the material feature trailed by the temperature outcome, owed to its superior impact on the formation of point defects and shear strain during tensile characterization.

scholarly journals A Review on the High Temperature Strengthening Mechanisms of High Entropy Superalloys (HESA)

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5835
Author(s):  
Malefane Joele ◽  
Wallace Rwisayi Matizamhuka
Keyword(s):  
High Temperature ◽  
Configurational Entropy ◽  
Extended Period ◽  
Theoretical Models ◽  
Intermetallic Phases ◽  
Processing Route ◽  
Strengthening Mechanisms ◽  
High Entropy ◽  
Use Of Resources ◽  
The Impact

The studies following HEA inceptions were apparently motivated to search for single-phase solid solution over intermetallic phases, accordingly made possible by the concept of high configurational entropy. However, it was realised that the formation of intermetallic phases in HEAs is prevalent due to other criterions that determine stable phases. Nonetheless, recent efforts have been directed towards attributes of microstructural combinations. In this viewpoint, the techniques used to predict microstructural features and methods of microstructural characterisation are elucidated in HESA fields. The study further analyses shortcomings regarding the design approaches of HESAs. A brief history is given into how HESAs were developed since their birth, to emphasize the evaluation techniques used to elucidate high temperature properties of HESAs, and the incentive thereof that enabled further pursuit of HESAs in the direction of optimal microstructure and composition. The theoretical models of strengthening mechanisms in HEAs are explained. The impact of processing route on the HESAs performance is analysed from previous studies. Thereafter, the future of HESAs in the market is conveyed from scientific opinion. Previous designs of HEAs/HESAs were more based on evaluation experiments, which lead to an extended period of research and considerable use of resources; currently, more effort is directed towards computational and theoretical methods to accelerate the exploration of huge HEA composition space.

scholarly journals Designing order–disorder transformation in high-entropy ferritic steels

2021 ◽  
Author(s):  
Prashant Singh ◽  
Duane D. Johnson
Keyword(s):  
Short Range ◽  
Density Functional ◽  
Short Range Order ◽  
Range Order ◽  
Atomic Scale ◽  
Atomic Fraction ◽  
Compositional Variation ◽  
Ferritic Steels ◽  
Chemical Inhomogeneity ◽  
High Entropy

AbstractOrder–disorder transformations hold an essential place in chemically complex high-entropy ferritic steels (HEFSs) due to their critical technological application. The chemical inhomogeneity arising from mixing of multi-principal elements of varying chemistry can drive property altering changes at the atomic scale, in particular short-range order. Using density-functional theory-based linear-response theory, we predict the effect of compositional tuning on the order–disorder transformation in ferritic steels—focusing on Cr–Ni–Al–Ti–Fe HEFSs. We show that Ti content in Cr–Ni–Al–Ti–Fe solid solutions can be tuned to modify short-range order that changes the order–disorder path from BCC-B2 (Ti atomic-fraction = 0) to BCC-B2-L21 (Ti atomic-fraction > 0) consistent with existing experiments. Our study suggests that tuning degree of SRO through compositional variation can be used as an effective means to optimize phase selection in technologically useful alloys. Graphic abstract

scholarly journals Effect of Mo Addition on The Microstructure and Mechanical Properties of CoCuFeNi High Entropy Alloy

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1017
Author(s):  
Yang Shao ◽  
Huan Ma ◽  
Yibing Wang
Keyword(s):  
Mechanical Properties ◽  
Solution Structure ◽  
Tensile Tests ◽  
Atomic Ratio ◽  
Vacuum Arc ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Microstructure And Mechanical Properties ◽  
Mo Content

In order to reveal the effect of Mo addition on the microstructure and mechanical properties, (CoCuFeNi)100-xMox (x = 0, 10, 15, 19, and 25, x values in atomic ratio) high entropy alloys were prepared by vacuum arc-melting. The results showed that with Mo addition, the μ phase formed and serious separation occurred in the high entropy alloys. The content of μ phase increased with the increase in Mo content. The microstructure of the alloys changed from an initial single-phase face-center-cubic (FCC) solid solution structure (x = 0) to a hypoeutectic microstructure (x = 15), then to a full eutectic microstructure (x = 19), and finally to a hypereutectic microstructure (x = 25). Coherent interface between μ phase and FCC phase was observed. The (CoCuFeNi)81Mo19 alloy with fully eutectic microstructures exhibited the highest yield strength of 557 MPa and fracture strength of 767 MPa in tensile tests at room temperature. The fracture surface revealed that the formation of great amounts of the μ phase resulted in the loss of ductility of (CoCuFeNi)100-xMox alloys.

Atomic-scale compositional characterization of a nanocrystalline AlCrCuFeNiZn high-entropy alloy using atom probe tomography

2013 ◽  
Vol 61 (12) ◽  
pp. 4696-4706 ◽  
Author(s):  
K.G. Pradeep ◽  
N. Wanderka ◽  
P. Choi ◽  
J. Banhart ◽  
B.S. Murty ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Atom Probe ◽  
Atomic Scale ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Compositional Characterization

scholarly journals Exploring the Relationship between the CO Oxidation Reaction and the Elemental Composition in Electrocatalysts with Machine Learning - a Case Study of PtRuPdRhAu High Entropy Alloys

2021 ◽  
Author(s):  
Vladislav Mints ◽  
Jack Pedersen ◽  
Alexander Bagger ◽  
Jonathan Quinson ◽  
Andy Anker ◽  
...  
Keyword(s):  
Machine Learning ◽  
Co Oxidation ◽  
Oxidation Reaction ◽  
Density Functional ◽  
Hydrogen Oxidation ◽  
Bayesian Optimization ◽  
High Entropy Alloy ◽  
Onset Potential ◽  
High Entropy ◽  
Co Oxidation Reaction

In recent years, the development of complex multi-metallic nanomaterials like high entropy alloy (HEA) catalysts has gained popularity. Composed of 5 or more metals, the compositions of HEAs exhibit extreme diversity. This is both a promising avenue to identify new catalysts and a severe constraint on their preparation and study. To address the challenges related to the preparation, study and optimization of HEAs, machine learning solutions are attractive. In this paper, the composition of PtRuPdRhAu hydrogen oxidation catalysts is optimized for the CO oxidation reaction. This is achieved by constructing a dataset using Bayesian optimization as guidance. For this quinary nanomaterial, the best performing composition was found within the first 35 experiments. However, the dataset was expanded until a total of 68 samples were investigated. This final dataset was used to construct a random forest regression model and a linear model. These machine learned models were used to assess the relationships between the concentrations of the consituent elements and the CO oxidation reaction onset potential. The onset potentials were found to correlate with the composition dependent adsorption energy of *OH obtained from density functional theory. This study demonstrates, how machine learning can be employed in an experimental setting to investigate the vast compositional space of HEAs.

scholarly journals Atomic-scale characterization and modeling of 60° dislocations in a high-entropy alloy

2016 ◽  
Vol 110 ◽  
pp. 352-363 ◽  
Author(s):  
T.M. Smith ◽  
M.S. Hooshmand ◽  
B.D. Esser ◽  
F. Otto ◽  
D.W. McComb ◽  
...  
Keyword(s):  
Atomic Scale ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Scale Characterization

A Density Functional Theory Study of the Hydrogen Absorption in High Entropy Alloy TiZrHfMoNb

2020 ◽  
Vol 59 (14) ◽  
pp. 9774-9782 ◽  
Author(s):  
Jutao Hu ◽  
Jinjing Zhang ◽  
Haiyan Xiao ◽  
Lei Xie ◽  
Huahai Shen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Absorption ◽  
Density Functional ◽  
High Entropy Alloy ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
High Entropy

scholarly journals Simultaneously enhancing the ultimate strength and ductility of high-entropy alloys via short-range ordering

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shuai Chen ◽  
Zachary H. Aitken ◽  
Subrahmanyam Pattamatta ◽  
Zhaoxuan Wu ◽  
Zhi Gen Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ultimate Strength ◽  
Short Range ◽  
Density Functional ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Body Center Cubic ◽  
Short Range Ordering ◽  
Composite Microstructure ◽  
Strength And Ductility

AbstractSimultaneously enhancing strength and ductility of metals and alloys has been a tremendous challenge. Here, we investigate a CoCuFeNiPd high-entropy alloy (HEA), using a combination of Monte Carlo method, molecular dynamic simulation, and density-functional theory calculation. Our results show that this HEA is energetically favorable to undergo short-range ordering (SRO), and the SRO leads to a pseudo-composite microstructure, which surprisingly enhances both the ultimate strength and ductility. The SRO-induced composite microstructure consists of three categories of clusters: face-center-cubic-preferred (FCCP) clusters, indifferent clusters, and body-center-cubic-preferred (BCCP) clusters, with the indifferent clusters playing the role of the matrix, the FCCP clusters serving as hard fillers to enhance the strength, while the BCCP clusters acting as soft fillers to increase the ductility. Our work highlights the importance of SRO in influencing the mechanical properties of HEAs and presents a fascinating route for designing HEAs to achieve superior mechanical properties.

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